With increasing development of information industries and high-tech industries, most precise electronic instruments and facilities need highly reliable power to maintain normal operations. Generally, an uninterruptible power supply (UPS) are widely used to provide stable power to the loads that are connected with the UPS. In other words, UPS apparatuses become essential for supplying stable power.
In other words, the uninterruptible power supply (UPS) is interconnected between a power source and a load. The power source may be a utility power source, an AC power source for providing a regulated AC voltage, or a DC power source for providing a regulated DC voltage. In a case that the power source is normal, the electrical energy provided by the power source will charge the backup battery. Once the power source is abnormal, the storage voltage of the backup battery will be converted into the rated voltage of the load for maintaining normal operations of the load.
For protecting important electronic devices in a more effective manner, the uninterruptible power supply is widely employed to assure normal operations of various electronic devices.
Recently, a high-capacity uninterruptible power supply is developed to increase the reliability and reduce the maintenance time. The high-capacity uninterruptible power supply includes plural power modules that are connected with each other in parallel. Generally, a controller is used to control operations of the plural power modules. In a case that one of the power modules is damaged, the uninterruptible power supply could still output stable power. Since the uninterruptible power supply has a single controller, if the controller is damaged, the plural power modules fail to be effectively controlled. In this circumstance, the output voltage is interrupted or abnormal, or even the load or the battery may be damaged to incur serious safety events. That is, the controller is an important device influencing the reliability of the uninterruptible power supply.
Recently, the controller of the uninterruptible power supply is gradually developed in a modular manner. If the modular controller is damaged, the modular controller could be quickly repaired to normally provide stable power. The modular controller, however, fails to increase the reliability of the uninterruptible power supply. If modular controller is damaged, the output voltage is still abnormal.
For increasing the reliability of the uninterruptible power supply, the uninterruptible power supply may be equipped with two controllers. One of the two controllers is responsible for controlling the power modules to output electrical energy. If this controller is damaged, the other controller will take some simple measures to maintain a constant output voltage and thus a sufficient time is provided to repair the damaged controller. Although the uses of two controllers may increase the reliability of the uninterruptible power supply, the additional controller increase the overall cost of the uninterruptible power supply.
Therefore, there is a need of providing an improved uninterruptible power supply so as to obviate the drawbacks encountered from the prior art.